SOLUTION: I have looked for this problem on this site but did not see it anyplace. Please help. Several of us cannot figure out how to work it. A man invests $8000 in savings for two year

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Question 187091: I have looked for this problem on this site but did not see it anyplace. Please help. Several of us cannot figure out how to work it.
A man invests $8000 in savings for two years. At the start of the second year he adds $2500 to the $8000. At the end of the second year the account balance is $11,445. What is the annual interest rate? Please help, there are three of us and we cannot figure it out.
Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!


At the end of the first year, he will have:



in his account. He adds $2500 at the beginnning of the second year:




So at the end of the second year he will have:



Which we are told is equal to 11,445, so:



Solve the quadratic for r to get your desired annual interest rate. Note, the quadratic will have two roots. One of them will be negative and is an extraneous root introduced by squaring the variable during the process of solving the problem. Exlude the negative root, and your positive root will be the solution you seek.

John